Boost converter for battery-powered rails
The 600 kHz switching frequency allows the use of small inductors and ceramic capacitors, keeping the total solution footprint compact. Synchronous rectification improves efficiency at lower output voltages compared to a diode-based boost, which matters when the output is close to the input voltage.
Voltage rails and load budget
The 1.8 A switch current is the peak current the internal NMOS switch can handle. For a given output voltage and load, the input current will be higher than the output current by the boost ratio divided by efficiency. A 3.3 V output at 500 mA from a 1.5 V input, for example, draws roughly 1.2 A from the input — leaving headroom below the 1.8 A switch limit.
The datasheet layout recommendation calls for multiple vias under the pad to a ground plane.